When used as a fuel for an internal combustion engine, compressed natural gas is supplied to the fuel metering device at a selected pressure in the range between atmospheric pressure and about 50 psig (between 0 and about 340 kPa gauge). A pressure regulator is required to reduce the fuel pressure from the storage pressure of between 50 and 2500 psig (340 kPa and 17 MPa gauge) to the desired supply pressure.
In order to provide accurate control of the supply pressure when the storage pressure varies over a 50 to 1 range (2500 to 50 psig; 17 MPa to 345 kPa gauge), prior engine fuel systems have employed an array of pressure regulators arranged in series to reduce the fuel pressure in steps from the storage pressure to the supply pressure.